The Sensata Dominican REP (or Mexico depending on where made) RP5A is a thermal protector* for lighting fixtures. It has a heater voltage of 120Vac and has low sensitivity. It has four leads, black, white, blue and red. When the temperature of the fixture is exceeded it will cause the light to blink. It is auto resetting for when the fault is corrected. The Sensata RP5A is designed to fit into a 1/2" KO.The Sensata RP-5A is a critical safety component specifically engineered for recessed lighting fixtures. As a self-resetting thermal protector, its primary function is to monitor the internal temperature of a light housing and detect the presence of dangerous insulation buildup. If the fixture exceeds safe operating temperatures—often caused by "overlamping" with a higher-wattage bulb than recommended or improper contact with attic insulation—the RP-5A interrupts the electrical circuit. This causes the light to blink repeatedly, providing a visual warning to the homeowner that a fault condition exists and preventing a potential fire. Designed with a compact, snap-in profile, it typically fits into a standard 1/2-inch knockout and features a 4-wire configuration suitable for multi-tap ballast applications.